OBJECTIVE: To assess the concentration of faecal elastase-1 (EL-1) in pediatric patients with cystic fibrosis with mutation DeltaF508.METHODS: Cross-sectional study with samples collected consecutively from 51 patients aged 4 months to 17 years old (mean 9.11±4.74); 32 (62.8%) patients were male. Clinical-demographic data were collected, as well as data on the type of mutation. Exocrine pancreatic insufficiency was established by the activity of faecal EL-1 < 200 µg/g. EL-1 was quantified through the monoclonal ELISA method (ScheBo Biotech AG, Germany). Pancreatic supplements were used in 46 (90.2%) patients.RESULTS: Forty-one (80.4%) patients presented with pancreatic insufficiency (EL-1 fecal < 100 µg/g): 17 (41.5%) were homozygous, 14 were heterozygous (34.1%) and 10 were non-DeltaF508 (24.4%). Regarding the mutation, there was a statistically significant association of homozygosity with faecal EL-1 concentration < 100 µg/g (p = 0.010). All patients considered to be pancreatic insufficient (n = 41) by the test were using pancreatic supplements. Ten (19.6%) presented faecal EL-1 > 200 µg/g, and 5/10 (50%) used enzymes.CONCLUSIONS: The activity of faecal EL-1 < 100 µg/g, indicating pancreatic insufficiency, was observed in 17/17 (100%) of homozygous patients, as expected, and was less frequent in patients who were heterozygous for DeltaF508 and in patients without the mutation. There was no association of faecal EL-1 concentration with age and sex of patients. The test was standardized, is easy to execute, and can be used to assess the pancreatic status of patients with cystic fibrosis.